Treatment of keratinous substrates

ABSTRACT

A process for the modification of monomerpretreated-keratinous substrates which comprises treating the keratinous substrate with a small but effective amount of a compound comprising a mercury salt of an organic carboxylic acid.

United States Patent A Gluseppe Anzuino Vercelli. Italy;

Clarence Ralph Robbins, Piscataway. NJ. 2,943 Jan. 14, 1970 Nov. 9, 1971 Colgate-Palmolive Company New York, N.Y.

Inventors Appl. No. Filed Patented Assignee TREATMENT OF KERATINOUS SUBSTRATES 12 Claims, No Drawings U.S. Cl 8/1275, 8/128, 8/127.51

Int. Cl D06m 3/00, D06m 3/02. D06m 13/00 Field of Search 8/ 127.5.

127.51.128. DIG. 18; 260/855 M; 424/71 Primary E.ran|inerGeroge F. Lesmes Assislan! Examiner-43. Bettis Auorneys Herbert S. Sylvester. Murray M. Grill. Norman Blumenkopf. Ronald 8. Cornell. Robert A. Burroughs. Thomas J. Corum. Richard N. Miller and Robert L. Stone ABSTRACT: A process for the modification of monomerpretreated-keratinous substrates which comprises treating the keratinous substrate with a small but effective amount of a compound comprising a mercury salt of an organic carboxyiic acid.

TREATMENT OF KERATINOUS SUBSTRATES The present invention relates, in general, to the treatment of keratinous substrates and in particular to the provision of novel means for synergistically enhancing the physical properties of a wide variety of keratinous substances such as typified by human hair, animal hair, wool and the like.

As is well known, keratinous substrates may be modified physically and/or chemically by suitable processing. Thus, the treatment of human hair for purposes of permanent waving as well as other conditioning constitutes well established technology, the relevant techniques being described in the published literature, both patent and otherwise. Thus, with reference to the treatment of human hair for purposes of imparting curl thereto, conventional processing involves a multistep procedure, the initial operation comprising solution impregnation of the hair fibers with a suitable medium, the reducing solution treatment serving to effect substantial reduction of the keratin material whereby to convert cystine linkages i.e., disulfide bonds to mercaptan. The desired modification of the fiber material is subsequently effected by treating the keratin mass with a suitable oxidizing solution in known manner. The processing solutions and materials required for the implementation of such techniques are likewise well known in the art, being available commercially in a wide variety of forms. Although keratin-modification methods of the aforedescribed type are exploited to a significant extent on a commercial scale, such methods have nevertheless been found in practice to be subject to one or more disadvantages which tend to detract considerably from their commercial desirability. Perhaps, the primary objection concerns the failure of such processing to provide a final hair set possessed of the requisite form-retention stability, the latter condition being essential as regards any possibility of atraining satisfactory hair flexibility and structural integrity devoid of undesired brittleness, hardness, etc. Other disadvantages found to characterize keratin-modification methodology heretofore provided include, for example, the objectionable tendency to yield a hair product of inferior body, thickness, luster etc. In practice, it has also been determined that many of the compositions incident to such processing e.g. permanent wave compositions, wave sets and the like, characteristically yield undesired film deposits which exhibit a highly objectionable tendency to flake off, dry to a hard friable deposit and/or discolor the hair as well as other physical impairment.

Nevertheless, the failure of the keratin-modification treatments heretofore described to provide a final hair set of optimum structural integrity i.e., in terms of elasticity, tensile strength, form-retention capacity, flexibility, resilience and the like has proved of paramount importance and continues to challenge the relevant technology.

As a result of the foregoing situation, considerable industrial activity has centered around the research and development of methods and compositions specifically and beneficially adapted for use in connection with techniques devised to enable purposive, predetermined modifications in the properties of keratinous substrates absent detrimental effects upon the strength characteristics of the fiber selected for treatment.

Thus, in copending application Ser. No. 829,097 there is described a multistep procedure for the treatment of keratinous materials whereby to achieve selective modifications in one or more properties, the involved process comprising the sequential steps of 1. reduction 2. rinsing 3. oxidation In accordance with such processing, initial reduction of the keration material is effected by treating same with a reducing solution for a time sufficient to permit substantial reduction of keratin substrate, the term reduction" here connoting the conversion of cystine linkages i.e., disulfide bonds to mercaptan. Upon completion of the desired extent of reduction, the keratin material is subjected to a thoroughgoing rinsing operation for purposes of completely removing residual-reducing agent. Intermediate rinsing comprises a particularly critical phase of the overall processing scheme, the improvements and advantages described depending pivotally thereupon. Upon completion of the rinsing step, the keratin material is subjected to oxidation with a solution comprising vinyl-type monomer in the presence of free radical-liberating catalyst whereby to attached polymerized monomer segments to the individual keratin fibers.

Another technique for effecting the modification of keratinous substrates is described in copending application Ser. No. 829,095, the salient characteristic of this particular method residing in the use of a highly specific catalyst material, namely persulfuric acid and/or its water-soluble salts. The use of this specific catalyst material obviates any necessity for the use of multistep processing while permitting realization of the desired degree of keratin modification. Thus, the contemplated objectives are achieved by the use of a single processing solution containing as essential ingredients the monomer material and persulfuric acid catalyst.

Yet, another technique for effectively modifying the properties of keratinous substances is that described in copending application Ser. No. 829,096. This particular method entails the significant advantage that polymer grafting can be synergistically enhanced or otherwise augmented by effectuating the monomer-treating operation in the presence of small but effective amounts of a water-soluble halide salt i.e., a salt of bromine with a water-solubilizing cation such as lithium, sodium, potassium, ammonium, substituted ammonium and the like. According to such processing, significant improvement in polymer takeup rate is attainable in the absence of adverse effects upon other properties considered desirable if not necessary in the keratin material.

Dissimilar but nevertheless somewhat analogous keratin treatment methodology is likewise described in the published literature both patent and otherwise. In the main, such processing involves as an essential expedient the treatment of wool or similar fabric with a reducing agent, such impregnation treatment being designed to deposit upon and within the fibers effective quantities of such reducing agent e.g., ferrous sulfate.

In any event, and regardless of the particular method employed for purposes of achieving monomer grafting to the keratin fiber it is nevertheless found, other attendant advantages notwithstanding thatthe beneficial effects are often vitiated due to markedly suboptimum strength properties and particularly wet strength properties in the keratin product, i.e., reference being made in this regard to tensile strength. The importance of the latter is largely self-evident and becomes manifestly clear when considered for personal wear. As will be recognized, even minor departures from optimum strength characteristics with such fabrics may suffice to vitiate any practical advantage which might otherwise be obtainable. Clearly, and especially with respect to garments designed for external wear, the matter of tensile strength is of vital importance bearing upon the appearance, useful life etc. of the garment. Considerations associated with structural integrity are likewise of primary importance in connection with techniques specifically adapted to enable the modification of hair whether of human origin or otherwise; accordingly, in the absence of the requisite degree of tensile strength, the final hair product will inevitably exhibit an untoward resistance to form manipulation e.g., bending, as well as minimal form retention stability with the consequent tendency to snag, snap, tear, etc. or otherwise result in an aesthetically displeasing appearance. The foregoing desiderate are, of course, highly inimical to expeditious hair management.

In an effort to overcome or otherwise mitigate the foregoing and related disadvantages, considerable industrial activity has centered around the research and development of keratinmodification techniques capable of providing a keratin product modified as desired and yet possessed of optimum strength characteristics and particularly tensile strength. Although much in the way of meritorious improvement has characterized such efforts, the overall improvement proves in most instances to be of marginal significance only. Thus, it is usually found in practice that the amelioration of problems associated with structural stability and integrity often leads to deleterious effects upon one or more of the other essential properties desired in the treated keratin material product. In addition, economic considerations alone may well be of such significance as to recommend against a given method thus necessitating resort to less costly albeit inferior techniques.

In accordance with the discovery forming the basis of the present invention, it has been ascertained that processing singularly and beneficially adapted for use in the treatment of keratinous substrates and involving the use of vinyl monomer capable of free radical-induced polymerization may be synergistically modified to advantage and thereby rendered more effective by the employment of a post-treating operation involving the subjection of the treated keratin substrate to a substance selected from a highly delimited class of materials, the latter serving to augment or otherwise enhance the structural integrity and particularly tensile strength of the treated substrate.

Thus, the primary object of the invention resides in the provision of an improved process for the treatment of keratinous substrates wherein the aforementioned difficulties and disadvantages are eliminated or at least mitigated to a substantial extent.

A further object of the present invention resides in the provision of a process for the treatment of modified keratinous substrates which makes possible the production of a final keratin product having exceptional structural integrity said process being effectively devoid of any tendency to disrupt or otherwise adversely affect the properties desired in the final keratin material selected for treatment.

A still further object of the present invention resides in the provision of a process for the post treatment of modified keratin substrates said process having exceptional utility in connection with the treatment of modified fibrous materials constituted wholly or partly of keratin whereby to render same more resistant to adverse environmental effects such as moisture, heat, and the like.

Other objects and advantages of the present invention will become more apparent hereinafter as the description proceeds.

The attainment of the foregoing and related objects is made possible in accordance with the present invention which in its broader aspects includes the provision of a process for the modification of monomer-pretreated keratinous substrates said monomer having at least one functional group capable of acting as an electron donor group in the formation of coordination complexes which comprises treating said substrate with a small but effective amount of a compound comprising a mercuric salt of an aliphatic, organic carboxylic acid. Otherwise stated, the process of the present invention comprises treating a keratinous substrate, the latter having been previously treated with a solution of the aforedescribed monomer(s) under catalytically induced polymerization conditions with said mercuric salt. In a further aspect, the present invention pertains to the products produced in accordance with the aforedescribed process. The post-treatment operation prescribed for use in accordance with the present invention is most efficaciously implemented subsequent to completion of the keratinous substrate monomer treatment. As will be appreciated, the results contemplated herein in nowise depend critically upon the particular point of time at which such post-treatment operation is effected; accordingly, mercuric salt treatment may be carried out immediately subsequent to monomer treatment or some period thereafter. The primary requirement, as will be made manifestly clear hereafter, it that the polymerized monomer fragment present in the keratin substrate selected for treatment he possessed of the capacity to coordinate with the mercuric compound.

The mercuric compounds contemplated for use herein may be selected from a relatively wide range of materials which may be generally described as comprising mercuric salts of aliphatic carboxylic acids such compounds being capable of liberating mercuric ion in aqueous media. The particular carboxylic acid moiety comprising the anion of the mercuric salt is not particularly critical apart from the requirement that such salt derivative exhibit substantial water solubility in acidified aqueous media. The particular aliphatic carboxylic acid in question is preferably saturated i.e., devoid of carbonto-carbon unsaturated e.g., ethylenic linkages. Moreover, such acid may be mono or polybasic thereby comprehending monocarboxylic acids, dicarboxylic acids etc. Particularly beneficial results are found to obtain with mercuric salts of those carboxylic acids containing from two to four carbon atoms e.g., mercuric acetate, mercuric propionate, etc. Other materials found to be eminently suitable for use in the practice of the present invention include the mercuric salts of such acids as, n-butanoic acid, n-butyric acid, isobutyric acid, npentanoic acid, n-hexanoic acid and the like. The anion moiety of the mercuric salt is preferably limited in terms of carbon content since water solubility, dispersibility etc. is a vital prerequisite. Of further consideration, apart from the solubility requirement tending to limit the nature of the carboxylic group stems from the penetrability" or diffusibility" aspect. Thus, it is of critical importance that the mercuric compound be capable of intimately contacting the entire extent of the keratin mass; since increasing the size of the molecular fragment constituting the anion portion of the mercuric salt compound correspondingly diminishes ease of penetrability, it is usually found beneficial to employ mercuric salts derived from carboxylic acids of lower carbon content. However, it is recognized that departures from the foregoing carbon content limitations may be feasible or otherwise dictated in certain instances as would be the case for example in utilizing auxiliary ingredients for purposes of promoting solubility and/or penetrability, diffusibility etc.; thus, such limitation is to be regarded as critical solely from the standpoint of assuring the obtention of optimum results rather than a limitation on operability. Accordingly, the term water solubility" as used in the context of the present invention in connection with the mercuric salt compound is to be accorded a significance consistent with water sensitivity of dispersibility. Thus, the requisite homogeneity of dispersion may be achieved with the less soluble mercuric salts by the use of suitable adjuvants e.g., emulsifying agents, suspending agents and the like. ln any event, for the vast majority of applications, mercuric compounds having substantial water solubility e.g., approximately 20-25 percent at 10 (3. are recommended and preferred.

The mercuric salt when added to aqueous media may actually be present to some extent as an aqua-complex" as to be distinguished from the simple, solvated salt. Consequently, the term mercuric salt as used herein is likewise to be accorded a significance consistent therewith.

The mercuric salt is preferably introduced i.e., contacted with the monomer-treated keratin substrate in the form of an acidified aqueous solution in order to achieve the requisite intimacy of contacting. Solution concentration is largely a matter of choice the salient requirement imposed in this regard being that the mercuric salt concentration be tantamount to effective" quantities i.e., quantities conducive to the obtention of the desired degree of structural integrity. Thus, the particular proportions employed may range from a small but effective amount e.g., a 0.005 M molar solution to concentrations on the order of 0.6 M molar. it has been ascertained that optimum results obtain in those instances wherein the amount of mercuric acetate employed is sufficient to yield on a weight basis having reference to the total quantity of keratinous substrate employed, a ratio within the range of from about 3:1 to about 20:1. In some instances it may be desirable to avoid the use of more concentrated mercuric salt solutions; when so proceeding, it is advisable to limit the mercuric salt concentration to the lower ranges and merely repeat if necessary, contacting of such solution with the keratin material e.g., with successive replenished solutions. In those circumstances permitting the use of more concentrated solutions, the requisite quantity of mercuric salt may be introduced by the use of a single solution thereby obviating any necessity for the use of plural solution treatments, the latter proving rather burdensome from a materials-handling standpoint. Mercuric saltkeratin contacting is preferably carried out in acidified aqueous media; the specific pH value selected is not particularly critical provided that any incipient mercuric salt precipitation is minimized if not avoided altogether. Thus, relatively weak acid solutions i.e., thus having a pH substantially in excess of 4 to 5 may lack the requisite acidity to suppress or retard mercuric salt precipitation depending of course upon the nature of such mercuric compound. In any event, a pH value within the range of from about 2 to about 4.5 is recommended for optimum results. The necessary acidic pH can be supplied by the use of a suitable acid such as acetic, the organic carboxylic acids being preferred to the mineral acids in order to minimize any possibility of contamination. However, selection here lies largely within the discretion of the processor.

Duration of mercuric salt-keratin fiber contacting may vary within relatively wide limits having reference for example to the amount of polymer present in the keratin substrate, the overall efficiency of mercury salt-keratin contacting the concentration of mercuric salt in the treating solution, the penetrability or porosity of the keratin mass, temperature etc. Thus, periods ranging from as little as 2 minutes to 24 hours may be feasible in a given situation. Moreover, elevated temperature ranges are in no wise necessary or for that matter particularly recommended; thus, the mercuric salt treatment may be efficaciously implemented at room temperature. The actual period of contacting will likewise depend of course upon the extent of keratin modification desired; in some instances, only partial restoration of wet strength characteristics may be desired and thus, the mercuric salt-keratin contacting period can be adjusted accordingly.

In actual practice the fiber to be treated may be immersed in an acidified, aqueous solution of the mercuric compound for the desired interval under conditions promotive of uniform contacting of the mercuric compound with the entire keratin mass. Alternatively, the mercuric salt solution may be applied directly to the keratin mass as by spraying, mechanical applicator etc. this procedure being particularly feasible in those instances wherein the keratin fiber is to be partially treated i.e., only certain, predetermined areas. In view of toxicity problems, the processing of the present invention is primarily intended for use in connection with the treatment of materials constituted wholly or partly of keratin such as off-scalp i.e., nonliving human hair such as would be present in wigs and other forms of headdress, woolen garments and the like. By virtue of such processing, the specific material subjected thereto is characterized by markedly superior physical properties for example, garment wearability, resistance to humid environments and the like, while headdress articles so treated are possessed of greatly improved form stability e.g., curl retention stability, ease of manageability and manipulation etc. As mentioned previously, the keratin material contemplated for treatment in accordance with the present invention contains polymer fragments derived from monomer materials having at least one functional group capable of acting as an electron donor in the formation of coordination complexes e.g., with the mercuric compounds more fully described hereinbefore. Specific representatives of such functional groups include without necessary limitation, hydroxyl, carboxyl, nitrile, imide, amide, tertiary amino, carbalkoxy i.e., ester groups etc. As indicated, the mer units comprising the recurring moiety of the polymer fragment may be polyfunctional and thus contain more than one functional group. When present on adjacent carbons i.e., alpha-positioned functional groups, the improvements and advantages made possible by the present invention are even more markedly manifest apparently due to chelating effects. Keratin substrates found to be particularly beneficial for use in the practice of the present invention include those containing polymer fragments derived from the following monomer materials:

acrylonitrile ethylene glycol monomethacrylate acrylic acid methacrylic acid Z-dimethylamine ethyl methacrylate glycidyl methacrylate vinyl pyridine methyl methacrylate methyl acrylate ethyl acrylate butyl acrylate allyl acrylate butyl methacrylate isobutyl methacrylate t-butyl methacrylate allyl methacrylate 3,4-butenyl acrylate 2-hydroxypropyl methacrylate 3-hydroxypropyl methacrylate 2,4-dihydroxybutyl methacrylate acrylamide N,N-diethyl-methacrylamide N,N-dipropyl acrylamide N,N'-ethylene-bis-(N,N'diethyl) acrylamide As will be appreciated, in those instances wherein the keratin substrate has been treated with monomeric materials of the polyfunctional type e.g., those materials containing more than one vinyl-type grouping such as, allyl methacrylate, divinyl benzene and the like, considerable polymer cross linking may occur supplementary to the predominant graft copolymerization action as a result the polymerization-inducing oxidation treatment. This result obtains of course since monomers of this nature possess more than one group capable of undergoing polymerization under the reaction conditions employed. It will be understood that the present invention contemplates the treatment of keratin substrates containing polymer fragments derived from admixtures comprising two or more of such monomers. In such instances, it is required that at least one of the monomer materials possess at least one coordination complex forming a group of the type hereinbefore defined, such monomer comprising at least 10 percent on a molar basis of the monomer admixture. No such requirement is imposed as regards the nature of the other monomeric components of the admixture.

Processing in accordance with the present invention is found to be particularly beneficial when the prescribed keratin post-treatment operation is effected with keratin substrates having been subjected to the monomer treatment operation described in copending applications Ser. Nos. 829,095, 829,096 and 829,097 i.e., in the presence of free radical liberating catalyst or initiator. Catalyst materials suitable for such use and described in such aforereferenced copending applications include, without necessary limitation, cumene hydroperoxide, hydrogen peroxide, benzoyl peroxide, acetyl peroxide, tertiary butyl hydroperoxide, alkali metal salts of peroxides, alkali metal and ammonium salts of peracids such as peracetic acid, perbenzoic acid, persulfuric acid etc. According to the procedure described in copending application Ser. No. 829,097, particularly beneficial results as regards rate of monomer takeup are obtainable with the use of organosoluble initiator compounds such as typified by cumene hydroperoxide. In any event, selection of a given catalyst system will depend, inter alia, upon the solubility characteristics of the monomer involved, solvent system employed etc. Thus, the catalyst material in a given instance may exhibit substantial water solubility or organosolubility depending upon the factors mentioned.

In any event, it is of utmost importance to note at this juncture that the particular means employed for introducing the monomer substance into the keratin substrate in the form of polymerized monomer fragments is of secondary importance since the present invention may be advantageously applied in connection with the treatment of keratinous substrates containing polymerized products having functional groups possessing electrons capable of being donated to an acceptor cation i.e., mercury. The procedures delineated in copending applications Ser. Nos. 829,095, 829,096 and 829,097 warrant particular mention herein in view of their outstanding capability of providing a keratin substrate possessed of optimum properties in a wide variety of aspects. However, such reference should not be interpreted as being tantamount to limitation thereto. Indeed, the contrary situation obtains since the efficacy of the subject invention extends to monomertreated keratin substrates characterized as defined as regards polymer content regardless of the particular means availed upon whereby to accomplish such monomer pretreatment.

The process described herein may be effectively applied to a relatively wide variety of keratinous materials including for example various types of hair e.g., camel hair, mohair, horse hair, cattle hair, off-scalp human hair etc., fabric materials constituted wholly or partly of wool and the like. As is well known, keratin materials are categorized among the proteins containing varying quantities of chemically combined sulfur the latter being present in the protein molecule in the form of disulfide groups also referred to as cystine linkages. Thus, the amino acids are linked through amino groups to form long chain structures known as polypeptides the latter in turn being mutually interconnected through disulfide linkages. Thus, according to the procedures described in copending application Ser. Nos. 829,095, 829,096 and 829,097 the disulfide linkages i.e., S-S bonds are converted into thiol groups attached to polypeptide chains, interreaction of the peroxide initiator and the thus-formed thiol groups culminating in the formation of free radical species the latter serving as the polymerizationinitiating agency.

The following examples are given for purposes of illustration only and are not to be considered as necessarily constituting a limitation on the present invention. In the examples, all parts and percentages given are by weight unless otherwise indicated.

in the following examples the keratin substrate employed, where human hair, is from brown caucasian human hair (nonliving) and where wool, 64s Merino dry-combed top wool. The polymer material is introduced into the keratin substrate in the following manner. Single fibers, hair or wool, are immersed in a 6 percent ammonium thioglycolate solution (pH 9) for about 3 minutes, washed in deionized water and then immersed in a water-alcohol mixture of vinyl monomer (10 percent) and cumene hydroperoxide (4 percent) for 60 minutes at room temperature. Sufficient alcohol is added to the system to completely solubilize the hydroperoxide and monomer ingredients. The amount of polymer introduced into the fiber is calculated by weight pickup as determined in a dry box. The post-treatment operation is carried out by immersing the thus-treated fiber in the solution of mercuric compound having the concentration specified for the time period indicated.

EXAMPLES 1-6 In these examples the keratin fiber selected for treatment comprises human hair as described. Stress-strain properties are determined with respect to the polymer-containing hair fiber both prior to (calibration) and following mercuric acetate treatment in order to enable a comparative evaluation of the resultant wet strength properties. Calibration is carried out by placing the hair sample on a cellulose acetate tab and immersing same in deionized water at room temperature for a period of l to 2 hours. Thereafter, the hair fiber specimen is stretched to percent of its original length on an lnstron tensile tester at a rate of extension of 0.2 inch per minute. The fiber is then relaxed in water for l hour, dried, out from the tab and weighed. The post-relaxation step serves to completely restore the strength properties of the hair sample to the original, prestretching values. The hair fiber is then immersed in an aqueous solution of mercuric acetate acidified to a pH of 3.5 with 0.1 N acetic acid having the mercuric concentration specified. The hair sample is again stretched in the Instron tester in the manner described. The changes in wet strength properties are calculated by comparison of the data obtained from the calibration and mercuric acetate treatments. Positive percentage values signify increases in the corresponding property.

In each of the examples, the polymer-containing hair fiber sample is derived by graft polymerization with dimethyl amino ethyl methacrylate, the amount of polymer introduced being calculated by weight difierence. The results of the various treatments are summarized in table 1.

Wherein We represents work to 20 percent extension, Hl. represents HOOKEAN limit and F represents force to 20 percent extension.

As the foregoing data makes manifestly clear, significant increases in the wet strength properties of the hair fiber sample are achieved despite the use of relatively minor concentrations of mercuric acetate. At this point it should be mentioned that an 18 percent increase in a given property corresponds to total restoration of the original wet strength parameters. The net change in properties, using as a basis the natural or untreated i.e., nonmonomer treated fiber can be derived by the following equation: X=0.859 Yl5.7 wherein X represents the total change from the grafted state and l the total change from the untreated state. The values reported in table 1 represent of course changes from the grafted state.

In general, increasing the concentration of mercuric salt within certain limits leads to corresponding enhancement of the wet strength parameters.

EXAMPLES 7-12 The procedure outlined in connection with examples l-6 is repeated. The results obtained are summarized in table 2.

As will be noted, yet further increases in wet strength properties are achieved by virtue of employing the mercuric acetate compound in more concentrated form. Of further significance is the fact that the improvements realized in connection with a hair fiber devoid of polymer is of marginal significance only tending to confirm the overriding importance EXAMPLES 13-17 The procedure of examples l6 is repeated but wherein the concentration of mercuric acetate in the treatment solution is further increased. The results obtained are itemized in table 3.

TABLE 3 0.10 M Hg crncoo Ex polydimethylamino- No ethyl methacrylate We 70 HL F As is the case with examples 1-12, the percentage values summarized represent changes from the polymer-grafted state. As was the case with the previous examples significant improvement in wet strength properties is achieved by virtue of the involved treatment i.e., manifold increases in the wet strength parameters.

The significance of the foregoing results can be readily translated in practical terms; thus, the greater wet strength is manifested in the form of exceptional fiber structural stability e.g., resistance to strength dissipating or disrupting forces etc.. the fiber thus provided being readily and easily manipulated to form stable, arcuate i.e., curled configurations.

Several factors have been determined to influence the efficacy of the described process with perhaps the more important being of course the coordination capability of the functional group present in the polymer as well as the ease of penetration of the mercuric salt solution into and throughout the keratin mass. Thus, as the amount of polymer is increased to excessively high values there results a corresponding decrease in penetraility and a correlative diminution in the net improvement realized for equivalent modes of proceeding i.e., time of treatment, concentration of treating solution etc.

One of the salient advantages provided by the present invention relates to the fact that processing in accordance therewith not only enables complete restoration of wet strength properties but moreover, can actually provide a final keratin product having wet strength properties vastly superior to those characterizing the untreated state. In this connection, note the results obtained in examples l0, 1 l and 12 and specifically, the percentage improvement in work elongation and HOOKEAN limit.

As previously mentioned the duration of mercuric treatment may vary within relatively wide limits. This aspect is illustrated by the following examples. The processing described in connection with examples 16 is repeated with hair fibers containing 9.6-l0.6 percent of poly (dimethylamino ethyl methacrylate) such fibers being treated with a 0.1 M solution of mercuric acetate in 0.1 N acetic acid (pl-1 2.5) at a room temperature for the time periods indicated. The results obtained are summarized in table 4.

TABLE 4 Ex. Time of Reaction No. (Minutes) We HL 1' F,

18 5 +2120 +2780 +1975 l9 l0 +3036 +3013 +3153 20 2O +3134 +3145 +3106 21 3S +4753 +5650 +4605 22 60 +6400 +8705 +5794 23 150 V +6161 +8559 +6510 As the foregoing data makes clear, the reaction is rapid and for all practical purposes completed in a period of 60 70 minutes i.e., increases in time of treatment beyond such limits fails to provide commensurate increases in the wet strength parameters.

The process of the subject invention is applicable to keratin substrates containing polymer fragments derived from a wide variety of monomer materials, the sole requirement imposed being, as previously explained, the presence of at least one functional group capable of acting as a donor group in the formation of coordination complexes. The following examples are illustrative.

EXAMPLES 24-28 The process of examples l6 is repeated except that the polymer material present in the hair fiber comprises polyacrylic acid (PAA), polymethacrylic acid (PMA), polyacrylonitrile acid (PAN), polyethyleneglycol monomethacrylate (PEGM) and a copolymer of methacrylic acid and dimethylaminoethylmethacrylate (PMA+PDEM) respectively. In each case, mercuric acetate treatment is carried out for the time period in dicated utilizing a 0.05 M mercuric acetate solution (aqueous) acidified to a pH of 2.5 with acetic acid. The result obtained are itemized in the following table.

As the preceding date makes manifestly clear, the improvements provided by the present invention are not limited to a particular polymeric material assuming the presence of course of the required functional groups; thus, apart from such requirement, the specific chemical nature of the polymeric material is relatively unimportant.

In addition to hair, the subject invention is beneficially adapted for the treatment of wool as will be illustrated by the following examples.

EXAMPLES 29-32 Single Merino wool fibers, containing 45.64 percent of poly (dimethylamino ethyl methacrylate), after being calibrated in water at 20 percent extension are treated for 1 hour at room temperature with a 0.1 M solution of mercuric acetate in 0.1 N acetic acid (pH 3.0). The fibers are then soaked in water and stretched in identical manner. The results, taken as an average, are summarized in the following table 6.

TABLE 6 No. 7r We k HL 7: F,

Again, such results establish the manifold improvement in wet strength properties afforded by the instantly described processing with respect to wool as well as hair, From a practical standpoint, the structural improvements realized are manifested in the form of superior wearability, toughness as well as appearance.

Results similar to those described in the foregoing examples are obtained when the procedures described therein are repeated but employing as the substrate, a keratin material con taining polymer derived from one or more of the following monomer materials:

methyl methacrylate isobutyl methacrylate 3,4-epoxybutyl methacrylate Z-hydroxypropyl methacrylate 2,4-dihydroxybutyl methacrylate methacrylamide 4-vinyl pyridine N,N-dipropylacrylamide N ,N '-ethylene-bis-( N,N'-diethyl) acrylamide allyl methacrylate In each case, substantial improvement in wet strength properties is obtained. However, when employing acrylic-type monomers, it is usually advisable to employ more highly concentrated mercuric salt solutions and/or to prolong the mercuric salt-keratin contacting time, this being found necessary in view of the somewhat inferior tendency of estergroups to coordinate with the mercuric salt compound.

Moreover, other mercuric salts of aliphatic carboxylic acids may be used with equivalent advantage including for example mercuric propionate, mercuric butyrate, as well as mercuric salts of dicarboxylic acids. Such compounds are found to provide significant improvement in wet strength properties of keratin substrates when used either singly or in admixtures comprising two or more thereof. As previously mentioned, the

essential criteria is that the mercuric salt possess substantial water solubility, dispersibility, etc. this being more conducive to efficient contacting with the keratin material.

What is claimed is:

1. In a process wherein a keratin substrate is polymerized with a vinyl monomer, having at least one functional group capable of acting as an electron donor group in the formation of coordination complexes, under free radical induced polymerization conditions, the improvement which comprises post treating said modified substrate with a small but effective amount of an aqueous solution comprising a mercuric salt of a water-soluble aliphatic carboxylic acid, said treatment being carried out at an acid pH.

2. A process according to claim 1 wherein said acid pH is within the range of from about 2 to about 4.5.

3. A process according to claim 1 wherein said mercuric salt comprises mercuric acetate.

4. A process according to claim 1 wherein said keratin substrate comprises off-scalp human hair.

5. A process according to claim 1 wherein said keratin substrate comprises wool.

6. A process according to claim 1 wherein said monomer comprises acrylonitrile.

7. A process according to claim 1 wherein said monomer comprises ethylene glycol monomethacrylate.

8. A process according to claim I wherein said monomer comprises methacrylic acid.

9. A process according to claim 1 wherein said monomer comprises methyl methacrylate.

10. A process according to claim 1 wherein said monomer comprises acrylic acid.

11. A process according to claim 1 wherein said monomer comprises dimethylaminoethyl methacrylate.

12. A product produced in accordance with claim 1.

* l t i 

2. A process according to claim 1 wherein said acid pH is within the range of from about 2 to about 4.5.
 3. A process according to claim 1 wherein said mercuric salt comprises mercuric acetate.
 4. A process according to claim 1 wherein said keratin substrate comprises off-scalp human hair.
 5. A process according to claim 1 wherein said keratin substrate comprises wool.
 6. A process according to claim 1 wherein said monomer comprises acrylonitrile.
 7. A process according to claim 1 wherein said monomer comprises ethylene glycol monomethacrylate.
 8. A process according to claim 1 wherein said monomer comprises methacrylic acid.
 9. A process according to claim 1 wherein said monomer comprises methyl methacrylate.
 10. A process according to claim 1 wherein said monomer comprises acrylic acid.
 11. A process according to claim 1 wherein said monomer comprises dimethylaminoethyl methacrylate.
 12. A product produced in accordance with claim
 1. 